1. Field of the Invention
This invention relates to a printing device, having an electro-photographic arrangement having a photoconductor, to which a photoconductor drive motor and an exposure unit are assigned, and having a conveying device for the substrate to be imprinted, to which a conveying device drive motor is assigned, wherein the photoconductor drive motor and the conveying device drive motor can each be controlled by a control device and can be adjusted for a rotary motion and conveying motion of identical lengths, which are matched to each other.
2. Discussion of Related Art
Such printing devices are known from Patent Abstracts of Japan, vol. 013, no. 073 (P-830), Feb. 20, 1989 (Feb. 20, 1989) and Japanese Patent Reference 63 259576 A (Ricoh Co., Ltd), Oct. 26, 1988 (Oct. 26, 1988), as well as from U.S. Pat. No. 5,543,894. Although a synchronization of several movement sequences in these known printing devices is achieved, this requires either an elaborate control installation with individually adjustable set value transducers, or a central master controller, wherein the guide function is provided to a closed control loop of one drive mechanism, which in the end does not assure an equal influence of the printing process in all control loops.
As European Patent Reference EP 0 973 072 A1 shows, it is also known in connection with such a printing device to regulate the transporting speed of a conveyor belt for the substrate to be imprinted to a constant speed, and during this to scan time markers, which are fixedly applied to the conveyor belt.
Finally, a printing device can be found in Patent Abstract of Japan, vol,. 014, no. 445 (P-1110), Sept. 25, 1990 (Sept. 25, 1990), and Japanese Patent Reference 02 176673 A (Ricoh Ltd. ), July 9, 1990 (July 9, 1990), wherein drive motors for the photoconductor and a transport device are also provided. Here, one drive motor is assigned the guide role. Reference signals are derived from this drive mechanism, by which the other drive mechanisms are syncrhonized.
It is one object of this invention to provide a printing device of the type mentioned above but wherein the synchronization of the drive mechanisms occur along with an equal guide roll, and the common central control leads to clear, easily adjustable control devices.
According to this invention, this object is achieved with an incremental transducer or a pulse former assigned to each one of the photoconductor drive motor and the conveying device drive motor. By way of signaling paths the incremental transducers or the pulse formers provide the actual value signals of the motor for the rotary movement of the photoconductor drive motor and the conveying movement of the conveying device drive motor to a common master-slave controller, which adjusts the control devices of the photoconductor drive motor and the conveying device drive motor to a rotary speed and conveying speed which are matched to each other, synchronizes them and provides the control devices of the photoconductor drive motor and the conveying device drive motor with appropriate control signals via set/actual value feed lines. The writing speed for the exposure device assigned to the photoconductor is also derived from the regulated control signal fed back from the photoconductor drive motor.
Both drive mechanisms provide actual motor values to the common master-slave controller independently of each other which, knowing the drive circuits and associated control devices, issues control signals which are synchronized and matched to the drive circuits. The setting to a set value takes place centrally in the master-slave controller, and both drive systems are treated equally.
The design of the drive circuits of this invention is simple and clear.
The control can be performed simply in such a way that the control devices of the photoconductor drive motor and the conveying device drive motor regulate the motor voltage.
In accordance with one embodiment, for the derivation of simple-to-represent motor actual values the motor actual value signals of the photoconductor drive motor and the conveying device drive motor can be derived by resolvers, which electrically control the assigned pulse formers.
If incremental transducers are used, the incremental transducers are mechanically coupled with the photoconductor drive motor and the conveying device drive motor.
The master-slave controller permits a simple presetting of operating data, because the master-slave controller has an interface for a programming field, or its own programming field, by which the control parameters for the control devices can be input and changed.
According to further embodiment, for setting the exposure device the control signal from the master-slave controller for the photoconductor drive motor can be provided to the exposure device processed by a personal computer and a controller.
This invention is explained in greater detail in view of an exemplary embodiment represented in the drawing which shows a wiring diagram of a control arrangement for an electro-photographic copier.